Premium
Imaging Mass Spectrometry ‐ The Pyrazinamide Enigma
Author(s) -
Prideaux Brendan,
Sarathy Jansy,
Via Laura,
Gopal Pooja,
Barry Clifton,
Dick Thomas,
Dartois Veronique
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.503.2
Subject(s) - pyrazinamide , in vivo , tuberculosis , medicine , drug , pharmacology , extracellular , drug resistance , pharmacokinetics , intracellular , immune system , antibiotics , immunology , pathology , mycobacterium tuberculosis , microbiology and biotechnology , chemistry , biology , genetics , biochemistry
Pyrazinamide is a 60‐year old anti‐tuberculosis (TB) drug, the mechanism of which has been the focus of intense research and yet largely remains a mystery. Today, PZA would fall under the category of fragment rather than drug, and would likely be missed because it is not active under standard in vitro conditions despite its remarkable sterilizing activity against human TB. At the time of its introduction, PZA reduced therapy duration from 9 to 6 months, and has been part of the first‐line and most second‐line drug regimens since then. However, resistance to PZA continues to emerge, threatening one of the most valuable drugs in our current arsenal. Given the striking disconnect between PZA's activity in vitro and in vivo, we have developed pharmacological tools to study the pharmacokinetics, tissue distribution, metabolism, and activity of PZA at the site of action, in patients and in animal models. In pulmonary TB, the pathogen is both intracellular and extracellular, and resides in multiple types of lung lesions that essentially comprise layers of immune cells often surrounding necrotic foci. Decades of clinical trials have taught us that the presence of cavities – large necrotic lesions that are connected with an airway – correlates with poor treatment outcome. We also know that the spectrum of lesions seen in human TB is inhabited by multiple bacterial populations with differential susceptibilities to any given drug. We thus asked “which bacterial subpopulations are reached and killed by PZA?” Using MALDI mass spectrometry imaging and classical mass spectrometry, we have discovered that PZA and its active metabolite have the unique ability to distribute rapidly and homogeneously in all lesion types and lesion compartments, including cavities. Lesion‐centric efficacy studies in animal models have been conducted to measure the killing activity of PZA and its active metabolite POA against specific subpopulations, either in vitro or ex vivo. Characterization of resistant mutants isolated in vitro revealed complex metabolic networks affected by PZA's active metabolite. We will discuss what can be learned from these collective results to develop assays and screening strategies that have the potential to capture the “next‐gen PZA” and overcome ramping resistance.